Less than three weeks after being spotted on a romantic stroll in Hollywood, Katy Perry and John Mayer are suddenly over. There are already reconciliation rumors swirling, but Star can reveal that the breakup is much more serious, and that on at least one occasion last year, the 36-year-old cheated on the “Dark Horse” singer!

Katy was the one who decided to end things this time, possibly because she found out about John’s relationship with 24-year-old SoulCycle instructor, Lauren McHale. The pair met at a bar in Los Angeles last May, and went back to her house for a party after having a few drinks.

“They kissed,” an insider reveals. “It was very innocent. They didn’t sleep together.” Afterward, they texted for a few weeks, but haven’t seen each other since.

At the same time, John isn’t exactly torn up over being dumped — he’s gotten fed up with the 29-year-old’s partying and how she constantly wears a diamond ring on her left hand to create relationship buzz. “They have completely broken up and he’s moved out,” the source adds. “Katy is a wreck.”